1. SPP.org 1

2. 2 Aggregate Transmission Service Study (ATSS)

3. SPP.org 3 Overview of ATSS modeling

4. SPP.org 4 MDWG Model Overview Model Development Working Group (MDWG) produces an annual series of transmission planning models (16 Seasonal Cases representing 10 years) Siemens Model On Demand PSS™MOD is used MOD manages all Network Upgrades Network Upgrades included in STEP and ATSS models include approved SPP Transmission Expansion Plan (STEP), SPP Aggregate Study, and TO planned projects Network Upgrade In-service dates from Quarterly Project Tracking Reports (www.spp.org Engineering & Planning > Project Tracking)www.spp.org

5. SPP.org 5 STEP Reliability Model Overview STEP Base developed from MDWG Generation, Load, and Interchange projections backed by long term firm transmission rights. From STEP Base Five Scenarios developed  1 – West to East  2 – East to West  3 – South to North  4 – North to South  5 – All The scenarios are developed to minimize counter flows Scenario models include inter-area and some intra-area long term firm transmission rights reserved and renewal rights in excess of the projected schedules in the STEP Base

6. SPP.org 6 STEP Reliability Model Overview Scenario model determination done by using proxy flowgate analysis. Proxy flowgates used to determine scenarios are selected based on greatest historic and present Firm MWs Curtailed by NERC TLR. SPSNORTH_STH (North to South), SPPSPSTIES (East to West), HPPVALPITVAL (West to East), GENTLMREDWIL (North to South), COOPER_S (North to South), and BVSNBVNESDEL (South to North) Intermittent Wind Generation modeled at Reserved Amounts per Scenario model determination For Generation shortages – 1 st Local and remote generation historically used to serve load, 2 nd BA IPP generation, 3 rd all SPP IPP generation on a prorata basis

7. SPP.org 7 ATSS Model Overview Base case scenarios 1-5 developed equivalent to STEP models to include previous ATSS requests with “Study” status. Base cases sometimes referred to as reliability assessment models or pre-transfer cases From base case scenarios five study groups developed  1 – West to East  2 – East to West  3 – South to North  4 – North to South  5 – All The five groups are developed from the aggregate in order to minimize counter flows among requested service. Each request is included in at least two of the four groups depending on the requested path.

8. SPP.org 8 Transmission Request Modeling Point-To-Point Transmission Service requests are modeled as Generation to Generation transfers. Network Integration Transmission Service requests are modeled as Generation to Load transfers in addition to Generation to Generation transfers. Group Base Cases and Group Transfer Cases are created to perform the AC Transfer Analysis process. Siemens MUST used to perform transfer distribution sensitivity analysis using participations based upon merit order dispatch orders of Source and Sink Intermittent Wind Generation studied at Requested Amounts

9. SPP.org 9 AC Transfer Analysis Results Thermal and Voltage monitoring for System Intact and N-1 Contingency Analysis 3% TDF Threshold (No MW Impact Cutoff) 0.02 Power Transfer Voltage Factor TO Criteria used if more restrictive SPP PTDF Flowgates monitored No TRM on SPP Facilities First Tier Contingencies and Thermal Monitoring Coordinated Flowgates Monitored Contract Path Capacity Monitored Results can be found in the Aggregate Facility Data Log with upgrade assignment per limiting facility

10. SPP.org 10 Questions?

11. Chris Jamieson Lead Engineer Engineering, Tariff Studies 501-614-3231 cjamieson@spp.org cjamieson@spp.org